Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

=1

IEC

IEC exclusive-NOR gate (rectangular form)

An IEC exclusive-NOR is commonly drawn as the =1 element with a negation circle at its output. For two inputs, the output is active when both inputs are in the same state, which is why the function is also called equivalence. Some drawings instead use the = logic-identity qualifier, which gives the same two-input result.

Drawing use

Schematic

Application

Logic & signals

Reference family

IEC / Manufacturer

Form evidence

=1 element with output negation. Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.

A distinction that matters

The = identity element extends to many inputs as all-the-same; a negated =1 with three inputs means not exactly one active.

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XNOR

Symbols

Exclusive-NOR gate

For two positive-logic inputs, produces a true output when the input states are equal.

Drawing use

Schematic

Application

Logic & signals

Reference family

Manufacturer

A distinction that matters

XNOR specifies a logical function; an open-drain implementation is a separate electrical output characteristic.

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Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.